【作者】 王飞；

【导师】 程林；

【作者基本信息】 山东大学 ， 工程热物理， 2011， 硕士

【摘要】 板式换热器以其结构紧凑,性能优良,易清洗等优点,越来越广泛的应用于石油、化工、轻工、冶金、动力等工程领域,在整个国民经济和工业生产中对改善能源利用率,提高经济效益都起着举足轻重的作用,因此对板式换热器进行新板型的开发和优化设计,提高换热器整体性能就具有十分重要的现实意义和应用价值。本文采用数值计算的方法研究一种新型板式换热器—正六边形球面肋板式换热器,并在分析其内部传热和阻力特性的基础上进行优化设计,得到性能最优时的换热器参数。具体工作如下：首先,比较三种换热器评价标准：JF因子、熵产最小法和火积耗散原理,分析三种评价标准各自的物理意义及其在换热器中的应用情况,发现将JF因子作为基于热力学第一定律的性能评价标准是合适的；在热力学第二定律范畴内,火积耗散原理可以避免熵产最小法在实际应用中出现的矛盾和问题,本文将其推广应用到实际换热器的数值计算中。综合考虑各种影响因素,建立换热器计算模型,并搭建正六边形球面肋板式换热器水—水换热实验台进行实验验证,实验数据与数值计算结果吻合度较好,表明本文建立的计算模型能够准确预测换热器内部传热和流动情况,得到的数据是真实可信的。随后本文利用验证模型对正六边形球面肋板式换热器进行了传热和阻力特性研究,得到不同工况下换热器内部流场、温度场、压力场和火积耗散分布情况,探讨了板片结构对换热器性能的影响规律。发现火积耗散数忽略了阻力性能的影响,不适合单独作为换热器评价标准使用。并与一种传统人字形板式换热器进行性能比较,证实了正六边形球面肋板式换热器综合性能的优越性。最后,将球肋弧度和比例因子作为板片结构特征参数进行优化设计,得到了结构参数对换热器传热性能、阻力性能和火积耗散数的影响规律,提出火积耗散原理的优化方向为温度梯度最小,并不适合单独用于换热器新板型优化设计。因此采用JF因子作为主要优化目标,火积耗散数作为辅助优化目标,得到了最佳板片结构和运行参数。更多还原

【Abstract】 Plate heat exchangers(PHE) are more and more widely used in petroleum, chemical, light industry, metallurgy, power and other engineering fields with its advantages like compact structure, excellent performance, ease to clean, etc. It plays an important role in improving energy and economic efficiency of the whole national economy and industrial production. Therefore, it has important practical significance and applied value to design and optimize new PHE for improving the overall performance.In this paper, we investigate a novel PHE, Regular Hexagonal PHE with Spherical Ribs(RHPHE) by using numerical method, followed with the optimal parameter design through the analysis of its internal heat transfer and pressure drop characteristic, Which is specifically shown as follow:First, the physical meaning and the application in heat exchanger of three heat exchanger evaluation criteria, JF Factor, Entropy Minimization Method, and Entransy Dissipation Principle, are compared. JF Factor was found to be an appropriate criterion foras the First Law of Thermadynamics-based performance evaluation. In the context of the Second Law of Thermadynamics, Entransy Dissipation Principle avoided the contradictions and problems in practical application of Entropy Minimization Method. Then, we extend it to the actual PHE numerical calculation.Considering various influencing factors, we have established the PHE numerical model, and tested RHPHE in an experimental installation for experimenta verification. The experimental results fit well with the numerical results, which means the numerical model is reliable and can accurately predict the heat transfer and flow in RHPHE.Then, we use the verified model to study the heat transfer and pressure drop properties of RHPHE. Based on the obtained fluid flow and temperature, pressure, entransy distribution under different conditions, the effect of structure on entransy dissipation number is investigated. Results showed that the entransy dissipation number is not suitable as a separate heat exchanger evaluation criterion because of ignorance of the flow resistance. Compared with a traditional chevron PHE, RHPHE has a better overall performance.Finally, optimized design is carried on by chosing curvature and scale factor of spherical ribs as structural parameters. Effects of different structural parameters on heat tansfer performance, resistance performance, and entransy dissipation number distribution are studied. It is found that the optimal direction of the Entransy Dissipition Principle is to minimize the temperature gradient. So it’s not suitable for designing new plate type. Therefore, using JF Factor as main optimization objective, and Entransy Dissipation Number as auxiliary optimization objective, the optimal structural design and operating parameter of RHPHE are obtained.更多还原